Reactions of olefinic molecules in the presence of metal-containing catalysts to produce other olefinic molecules are known in the art as "disproportionation" reactions. A typical olefin disproportionation process is illustrated by U.S. Pat. No. 3,261,879, issued July 19, 1966, to Banks, wherein two similar non-symmetrical molecules of an olefin react in the presence of certain catalysts to produce one olefin of a higher carbon number and one olefin of a lower carbon number such as, for example, propylene disproportionation by the process of U.S. Pat. No. 3,261,879 to produce ethylene and butylenes.
As used in this application, disproportionation process means the conversion of olefinic hydrocarbons into similar olefinic hydrocarbons of higher and lower numbers of carbon atoms per molecule. Where the reactant comprises 1- or 2-olefins having relatively long chains, a mixture of products is obtained comprising primarily olefins having both a larger and a smaller number of carbon atoms than the feed olefin but also including other disproportionated products, for example, saturated hydrocarbons, and other converted and unconverted material. Such an operation is useful in many instances. For example, a more plentiful hydrocarbon can be converted to a less plentiful and therefore more valuable hydrocarbon. One instance of such a conversion occurs when the process of this invention is used to convert both higher and lower molecular weight olefins to olefins in the C.sub.10 -C.sub.16 range, a range of olefins especially suitable for the manufacture of detergents. Another instance of a disproportionation reaction having considerable value is the disproportionation of propylene to produce ethylene and butene.
A variety of catalysts have been employed for conducting disproportionation reactions, such as those disclosed in U.S. Pat. No. 3,340,322, issued Sept. 5, 1967., U.S. Pat. No. 3,637,892, issued Jan. 25, 1972; U.S. Pat. No. 3,760,026, issued Sept. 18, 1973; U.S. Pat. No. 3,792,108, issued Feb. 12, 1974., U.S. Pat. No. 3,872,180, issued Mar. 18, 1975., and British Pat. Specification No. 1,128,091, published Mar. 16, 1966.
It is also known that the presence of a catalyst which possesses double bond isomerization activity in a disproportionation process is advantageous because it increases the rate of conversion and makes possible the production of a wider range of symmetrical olefins such as butene-2. In addition, the isomerization activity permits the exhaustive cleavage of high molecular weight monoolefins with ethylene to lower molecular weight monoolefins such as propylene and isobutene. British Pat. No. 1,205,677, published Sept. 16, 1970, provides a catalyst which comprises an olefin disproportionation component and a Group VIII noble metal double bond isomerization component, i.e., palladium, platinum or ruthenium. Another catalyst system which accomplishes the same results is obtained by physically mixing catalytic magnesium oxide with tungsten oxide on silica catalyst. Other catalysts which have been developed include those obtained by copromoting an olefin disproportionation catalyst such as tungsten oxide on silica with minor amounts of the oxides of niobium, tantalum or vanadium to provide the double bond isomerization activity.
U.S. Pat. No. 3,786,112 discloses a catalyst comprising a physical mixture of an olefin disproportionation catalyst and a double bond isomerization catalyst wherein the double bond isomerization catalyst has been treated with an alkali metal or alkaline earth metal compound.
U.S. Pat. No. 4,180,524 discloses a single catalyst composition containing a support, uranium and at least one of molybdenum, tungsten or rhenium, which provides double bond isomerization activity as well as olefin disproportionation activity.
The catalysts in the above references are generally prepared according to conventional methods such as impregnation, wherein a carrier is impregnated with a solution of metals., co-precipitation, wherein a carrier compound and metals are simultaneously precipitated; or co-mulling, wherein dry powders are mixed with a suitable extrusion aid such as water and extruded. U.S. Pat. No. 4,754,099 is directed to a disproportionation process utilizing a cobalt/molybdenum hydrogel-derived catalyst.
The catalyst in the above references for isomerization and combined isomerization/disproportionation have either basic or neutral isomerization components. It has been found in the present invention that an acidic isomerization component in combination with a disproportionation component can be used for concurrent isomerization/disproportionation with a low side-product make, thus resulting in a greater quantity of useful olefins.